Ipico uses LF (low frequency) carriers for transmitters and receivers.  The reason for this is due to the wide wavelength which allows easier penetration of wet carbon based entities moving at relatively high speeds (i.e. sweaty athletes running).  We use two separate antennae lines in each mat, one for transmitting (charging) and one for receiving (listening).  There is an advantage to Dual Frequencies because it allows our readers to simultaneously charge and listen to tags.  All other passive systems (Championchip, DAG, Chronotrack, Winning Times, etc.) use a single line and alternate between functions.  In high density situations this can cause misses if the reader is charging when it should be listening and vice versa.  

EtherLynx Photo Finish Camera: ensure accurate results and a visual record record of every athlete crossing the finish line - a safeguard against transponder failure

IdentiLynx Video Camera: produce full-frame, time-synced video images that make verification of athlete identification easy

3. IPICO Transponder Technology: provide rapid, real-time athlete identification with the latest in RFID detection technology

We transmit at 125Khz which is a very isolated area in the spectrum. The only other radios in that space are maritime mobile communications. Generally not a problem in most environments. We receive at 6.8Mhz which has a wide enough bandwidth to accommodate many reads without data collision but is still very quiet.  It only shares space with aeronautical mobile communications.  When I say quiet, I mean a low noise floor.  The analogy I use to describe this involves, rather than a tag and a reader,  two people in a bar. If they are the only patrons they can talk to each other at a normal level.  The noise level is low. As more people enter the bar, the noise level raises and they have to talk louder to hear each other.  If, say, a band starts up they have to shout, repeat their messages often and still occasionally completely miss what the other is saying.  By selecting quiet operating bands with characteristics suited to our application we can overcome a lot problems.

There is a misconception that high frequency means high tech.  The higher the frequency the longer the read range.  The challenge in that case is when to attach the time stamp if the tag is first read 10M from the line.  It can also be trouble when you have separate lines close to each other and the readers pick up crossover. This is trouble in many triathlons because of the proximity of entry and exit in transition areas or out and back races with separate but adjacent start and finish lines.  As far as the time stamp trouble, some just read it when they see it.  The problem is that this varies with transmission strength, charge level, field time or environmental interference.  This often leads to a tag being seen and scored before a tag that was actually

ahead of it. Systems like Chronotrack monitors the signal strength of tag response and makes the assumption that the signal will be strongest when closest to the transmitter.  This can be a big problem in noisy environments. Also, the frequencies used in these applications are typically 13.6Mhz and 900Mhz, both of which are broadcast frequencies.  If a high powered transmitter for a radio down link or even a land mobile radio (i.e. security) can flood the receiver with noise which can cause misses.  Our systems charge and read the tag at the same time.  

Because of changing environmental, electrical and human conditions we still recommend backup lines.  Component variance, speed of the athlete, location of the tag and charge time can all affect the read rate so you will see all responsible timers using passive RFID, regardless of the manufacturer, employ backup mats.  By placing our backup lines 12 to 18 inches in parallel with the primary lines we can create a field about 3.5M deep. This ensures the tags remain in a charging field long enough to become fully energized.